In accordance with one embodiment, a sheet feed apparatus comprises a sheet housing section, a guide, an optical sensor, markers and a determination section. The sheet housing section houses sheets. The guide is arranged at a position corresponding to the size of the sheet housed in the sheet housing section. The detection position of the optical sensor varies by interlocking with the guide. The markers, which have different image features corresponding to the sizes, are arranged at the detection position of the optical sensor pre-determined according to the size of the sheet. The determination section determines the size of the sheet housed in the sheet housing section based on a detection result of the optical sensor.